Monthly Archives: March 2013

Kidneys: The Liquid Waste Disposal Plants of the Body

I am a “senior kittyzen,” and I’m proud of my advanced age and wisdom (really, I am).  One of the realities of senior kittyzenship, however, is that I have developed some chronic conditions (arthritis, for one; see my blog OUCH!).  I also have chronic renal insufficiency (CRI), which is an age-related degeneration of kidney function.  What, pray tell, do the kidneys do?  A LOT is the easy answer.  The longer answer is, well, considerably longer……

Let’s pretend that I am a town.  We’ll call me Elsie-opolis (I’m the capital of the universe!).  There are multiple parts to the town- the town hall (my brain); the telephone/DSL system (my spinal cord and nerves); the solid waste recycling plant (my GI tract); the watering recycling and liquid waste center (my kidneys); and so on.  So what exactly happens in the water recycling plant of Elsie-opolis?  First, the plant sends the incoming “dirty” water through a filtration device; this removes waste products (like BUN and creatinine- more on these later), as well as some water.  The second part of the filtration device helps recover the water that leaked through in the first step.  Along the way the recycling plant can change the balance of some things (like electrolytes), as well as reabsorb more of the water before sending it to the holding tank.  The holding tank then empties periodically.  So far, so good, but how does this explain kidney function?  Each part of the plant relates to part of the urinary tract; the initial steps (filtration, re-absorption of fluid, and electrolyte balance) occur in the kidneys.  The holding tank, or urinary bladder, then empties through a pipe (the urethra) to the outside world.

We’ll take the analogy one step further…. Say there’s a problem with the filters, or the area that pulls water out of the outgoing waste.  You end up with less waste being filtered, as well as more water being lost.  Same thing happens with kidneys that are sick- they don’t clean the blood as well, so waste products build up to higher levels in the blood (BUN and creatinine are the two major ones we track on blood work).  Sick kidneys also can’t reabsorb water as well, so more is lost in the urine.  This results in larger volumes of more dilute urine.  The electrolyte balance is also affected in the process, so you end up with too much of some things (like phosphorous) and too little of other things (like potassium).  Unfortunately, you can’t cure sick kidneys by changing a filter or flushing some pipes.  Kidney tissue doesn’t regenerate, so once it’s gone, it’s gone (kidney infections and some other kidney associated diseases are not in the same category- I’ll talk more about that in the future).  However, you can TREAT kidney insufficiency to slow progression of the disease and make life better for everyone involved.  See my future blogs about diagnosing and treating chronic kidney insufficiency (CRI).

This is my friend, Chunk, and his stuffed kidney toy.  It's never a bad idea to had an extra kidney sitting around, says Chunk!

This is my friend, Chunk, and his stuffed kidney toy. It’s never a bad idea to have an extra kidney sitting around, says Chunk!